1. Field of the Invention
This invention relates to the manufacture of pneumatic tires, particularly superlarge, heavy load tires typified by so-called OR tires. More particularly, it relates to a method of advantageously and simply manufacturing pneumatic tires having different tread patterns in the same newly-devised mold at the step of vulcanization building.
2. Description of the Prior Art
Among the heavy duty tires of this type, superlarge tires or OR tires are used in vehicles for self-running of public works and construction machines. The number of such tires in terms of production is fairly small as compared with TB tires for heavy load truck and bus. Moreover, the tires are different from each other in the required performances and application. However, meeting the delicate situation in accordance with these performance and application differences is difficult in view of economical reasons, so that the OR tires are uniformly manufactured having a few kinds of tread patterns. As a result, these tires are often obliged to be insufficient in required performance.
In general, a mold for tire building corresponds to one size and tread pattern of the tire and can merely be subjected to slight change in accordance with the presence of at most a sipe. On the other hand, the mold for superlarge tire such as OR tire amounts to several ten thousand dollars for each mold. Therefore, if the OR tires satisfy the different required performances in accordance with various applications, a considerably enormous cost is required in order to provide various tread patterns.